The basic principle of measuring astronomical atmosphere refraction

Abstract：The atmospheric refractive index anisotropy is a key problem in space geodetic technology.Several major obstacles resulting in no direct measurement of the astronomical refraction since a long time are analyzed in the view of astronomical observation, and necessary conditions now possessed to remove these obstacles are described.Based on special functions of the Lower Latitude Meridian Circle (LLMC) in Yunnan observatory, NAOC and according to a new instrumental error theory, a design plan of the special measuring instrument and a basic principle for measuring the refractions are presented.Long-term observed data indicate that it is feasible to determine instantaneous atmospheric refractions by the observation principle of the LLMC.Measured models of atmospheric refraction can be built consequently varied with change in observation station and azimuth.Furthermore, local measured refraction models in four directions of the east, west, south and north in Yunnan observatory are presented.

Keyword：astronomical refraction;measured model;Meridian circle;